Comment 21 for bug 767242

@AndreaZ: I have Dropbox installed and running and am not experiencing the issue. Before you removed Dropbox, did you try removing any other indicator? Just asking whether the issues disappeared because you removed Dropbox, or because you removed an (/any) icon...

I was experiencing the issue after setting 'desktop/unity/panel/systray-whitelist' to '[all]' (using dconf-editor). The issue stopped when I changed it to ['JavaEmbeddedFrame', 'Mumble', 'Wine', 'Skype', 'hp-systray', 'scp-dbus-service', 'tracker', 'Do', 'guake', 'SWT', 'update-notifier'].
I've now not seen the problem in weeks...

All the best
/N